I've noticed a few screenshots of terminal windows online which show thin highlighted edges around status bars or highlighted lines. In the following example, note the light grey edging around lines 1, 5, and 389:

In this example, notice the yellow edging around the Emacs mode line (status bar):

What is the name of this effect, and is it possible with iTerm 2 under OS X 10.10?
Update
After doing some research and digging into Emacs Customize interface theme code, I found some code that defined the edges. In Emacs parlance, it's called :box, and one of its attributes is line-width. Here's an example of a box line being defined in a theme:
'(modeline ((t (:background "Gray10" :foreground "SteelBlue" :box (:line-width 1 :style none) :width condensed)))) The documentation for :box can be found in the Emacs manual's face attributes documentation, though it doesn't mention how it works, or which terminals are supported.
I started to think that this might be a special feature of GUI versions of Emacs (such as Aquamacs, but I am pretty sure that I have seen screenshots of what appear to be Ubuntu Unity terminal windows with similar box highlights.

